1. Field of Invention
This invention pertains to an infusion device such as a patient controlled analgesic pump and the like with dual power supply, and more particularly to a microprocessor-controlled infusion device which can be powered by an AC supply, by rechargeable batteries, or by disposable batteries, and which device determines its supply automatically and adjusts its operation accordingly.
2. Description of the State of the Art
Infusion devices generally use two kinds of power schemes: disposable batteries, or AC power with rechargeable backup batteries. Disposable batteries are best for devices with low power consumption, which are moved frequently from one location to another, or which are not used on a continuous basis. AC systems with rechargeable batteries are best for continuous use or for applications where patient transport is limited. However, sometimes it is desirable to use the same device for both types of applications.
Frequently infusion devices are equipped with a power monitoring circuit which monitors the voltage level of the device power supply and activates an alarm when it senses a low power condition. However, rechargeable batteries and disposable batteries have different discharge characteristics, and therefore if the monitoring circuit is set to sense a voltage level appropriate for one of the batteries, the indication will not be effective for sensing the reserve power of the other type of battery.